rotax 912 vibration in low RPM

by yishai goldschmidt in General Tech Discussion 9 years ago

My rotax 912 vibrates below 2800 RPM
in normal speed it sowned wonderfool and have good prformance.
i balanced the carbs with vacum gauges.
any one have an idea?
yishai

Re: rotax 912 vibration in low RPM

by Roger Lee » 9 years ago

Roger Lee

131 5.38k 5.44k

My question first is; Are the carbs pneumatically synced down at idle (1700 ish, could be higher or lower) and up to around 3400-3500 rpm?

If not do this first then see what you have.

If your carbs are synced down around 1700 ish then I would want to make sure my friction check inspection on the gearbox is up where it is supposed to be (averages are around 420-485 in/lbs) and if the carbs are synced and you have a good gearbox check then I would to inspect the prop. I would check its tracking and make sure each blade had the same degree setting if it is adjustable. If all this is above is good then consider a dynamic prop balance.

Your ears cannot hear if the carbs are in sync unless the engine is so bad it vibrates badly and runs poorly.
Smooth running engines are very subjective and not objective.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

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